Thermostatic pressure transmitter

ABSTRACT

A temperature actuated pressure transmitter adapted to sense a temperature and transmit a proportional fluid signal. The transmitter includes a fluid pressure chamber, a cantilevered blade having a free end extended longitudinally adjacent said pressure chamber, a temperature sensing element adapted to transmit a force to said blade in response to a sensed temperature, and an exhaust nozzle assembly positioned in fluid communication with said chamber through which the fluid in said chamber can be exhausted. A valve member provided in an exhaust port of said nozzle assembly is engaged with the free end of said blade and is adapted to vary the rate of exhaust through said port and thereby vary the pressure in said chamber in accordance with the force transmitted to the valve member through the lever arm of said blade. The pressure in said chamber is thereby changed in proportion to the temperature sensed by said sensing means. In accordance with this invention, the nozzle assembly can be translated longitudinally with respect to the blade to adjust the span of the transmitter by adjusting the effective lever arm through which said blade operates against the valve member.

United States Patent Primary ExaminerWilliam E. Wayner Attorneys-Hume,Clement, Hume & Lee and James B.

Blanchard ABSTRACT: A temperature actuated pressure transmitter adaptedto sense a temperature and transmit a proportional fluid signal. Thetransmitter includes a fluid pressure chamber, a cantilevered bladehaving a free end extended longitudinally adjacent said pressurechamber, a temperature sensing element adapted to transmit a force tosaid blade in response to a sensed temperature, and an exhaust nozzleassembly positioned in fluid communication with said chamber throughwhich the fluid in said chamber can be exhausted. A valve memberprovided in an exhaust port of said nozzle assembly is engaged with thefree end of said blade and is adapted to vary the rate of exhaustthrough said port and thereby vary the pressure in said chamber inaccordance with the force transmitted to the valve member through thelever arm of said blade. The pressure in said chamber is thereby changedin proportion to the temperature sensed by said sensing means. Inaccordance with this invention, the nozzle assembly can be translatedlongitudinally with respect to the blade to adjust the span of thetransmitter by adjusting the effective lever arm through which saidblade operates against the valve member.

[72] Inventor Ernest.l.Duchek Prospect Heights, Ill. [21] Appl. No.811,526 [22] Filed Mar. 28,1969 [45] Patented May25, 1971 [73] AssigneePowers Regulator Company Skokie,ll1.

[54] THERMOSTATIC PRESSURE TRANSMITTER 7 Claims, 5 Drawing Figs.

[52] U.S.Cl 236/102, v 236/86,137/82 ,2 51/2 34 v [51] I nt.Cl 605d23/275 [50] FieldotSearch 236/86, 87, 79, 102, 99; 137/82 (X);251/234[56] References Cited UNITED STATES PATENTS 1,284,335 11/1918 Hodge236/86 1,503,971 8/1924 Bast 236/86 2,823,688 2/1958 Stokes et al 137/793,145,722 8/1964 Mueller 137/85 isl n l? 24 I PATENTEDHAY25I97I 3580.502

sum 1 [IF 2 I I n Attorneys THERMOSTATIC PRESSURE TRANSMITTER BACKGROUNDAND GENERAL DESCRIPTION This invention relates generally to pressuretransmitters and more specifically relates to a temperature actuatedpressure transmitter having a span adjustment feature.

It is well known in the art to use thermostatic pressure transmitterswhich sense a temperature and transmit a proportional pneumatic or othertype of fluid signal to some remotely located receiver gauge orindicator. Such assemblies are used in commercial installationsinvolving fans, compressors, air conditioning equipment and the like totransmit a fluid signal indicative of the temperature of theinstallation to a remote point.

One form of thermostatic pressure transmitter in current use includes ablade which is connected to a temperature sensing device and furtherengaged with the exhaust valve of a pressurized fluid system. Suchtransmitters create a pressure signal indicative of the temperaturesensed by the sensing device by varying the force transmitted to thevalve through the lever arm of the blade as a result of the applicationof a force to the blade by the temperature sensing device. The rate offlow through the exhaust valve and, therefore, the pressure in the fluidsystem are thereby varied in accordance with the temperature sensed bythe sensing device.

In the past, these blade-type thermostatic transmitters have beenprovided with various means to adjust the span of the transmitter, thatis, to adjust the change in output pressure per unit change in sensedtemperature. The span adjustment devices previously used in thesetransmitters generally have involved linkages and mechanisms devised inan attempt to effect a change in the force which the blade applies tothe exhaust valve of a fixed exhaust nozzle assembly. Such previousattempts to provide a span adjustment for blade-type transmittersgenerally have required complicated mechanical arrangements which addedmaterially to the production cost of the transmitter and which, in somecases, adversely affected the operation of the transmitter.

In accordance with this invention, the above problems in providing ablade-type transmitter with span adjustment means are alleviated byproviding the transmitter with a movable exhaust nozzle assembly. Bysuch an arrangement, the exhaust nozzle assembly can be translatedlongitudinally with respect to the blade member of the transmitter tochange the effective lever arm through which the blades acts upon theexhaust valve provided on the nozzle assembly. The problems incident todesigning span adjustment devices for use in transmitters having a fixednozzle assembly are thereby avoided, since this invention permits thespan of the transmitter to be adjusted easily by selectively moving thenozzle assembly longitudinally with respect to the blade.

Broadly described, the thermostatic pressure transmitter in accordancewith this invention comprises a blade-type transmitter having a movablenozzle assembly positioned adjacent the free end of the blade. A forcetransmitted to the valve of the movable nozzle assembly through thelever arm of the blade, in response to the temperature sensed by asensing element joined to the blade, thereby creates a pressure signalindicative of the sensed temperature. Further, movement of the exhaustnozzle assembly with respect to the blade varies the effective lever armof the blade and thereby adjusts the span of the transmitter.

Further objects and advantages of the present invention will becomeevident from the following description of two embodiments thereof, takenin conjunction with the drawings in which:

FIG. 1 is a plan view of one embodiment of the transmitter adapted to beactuated by a rigid bulb temperature sensing element, as viewed alongthe line 1-1 in FIG. 2;

FIG. 2 is an elevational view of the transmitter, as viewed along theline 2-2 in FIG. 1;

FIG. 3 is a cross-sectional elevational view of the transmitter, asviewed along the line 3-3 of FIG. I;

FIG. 4 is an enlarged fragmentary view of the movable exhaust nozzleassembly of the transmitter in accordance with this invention; and

FIG. 5 is a cross-sectional elevational view of a second embodiment ofthe transmitter adapted to be actuated by a remote bulb temperaturesensing element.

One embodiment of the temperature actuated pressure transmitter of theinstant invention is generally indicated by the reference numeral 10 inFIGS. 1-4. Generally, the transmitter 10 includes a base member 20 and aprotective cover plate 21. The base 20 defines an interior pressurechamber 22 at one end and a post member 24 at the opposite end. Thepressure chamber 22 is adapted to be connected to a fluid pressuresupply source through an upstream restriction (not shown), as well knownto those skilled in the art. As indicated in FIG. 2, a conduit 25defined in the base 20 places the chamber 22 in fluid communication withthe adjacent top surface of the base.

The transmitter 10 further includes a cantilevered blade 30. One end 32of the blade 30 is fixed to the post 24 on the base member 20, such asby screws 23, in a manner which prevents lateral movement of the blade.The blade 30 extends longitudinally from the post 24 so that its freeend 34 is positioned above the pressure chamber 22, preferably directlyover the conduit 25. The free end 34 of the cantilevered blade 30 isthereby free to move vertically toward or away from the conduit 25leading from the pressure chamber 22.

The transmitter 10 in accordance with this invention also includes atemperature sensing device 40. In the embodiment illustrated in FIGS.l4, the sensing device 40 comprises a conventional rigid bulb assemblyincluding bimetallic elements, such as the tubular element 42 and therod element 44. As well known by those skilled in the art, the elements42 and 44 have different coefficients of expansion and are capable ofmoving through a displacement which is proportional to the temperaturesensed by the elements.

The temperature sensing device 40 is rigidly secured to the transmitterbase 20 by means of a boss member 26 which receives the tubular element42. A vertical opening 28 in the base 20 allows the rod element 44 toproject upwardly through the base. As indicated in FIG. 2, the rodelement 44 also extends upwardly past the blade 30 through an aperture38 provided in the blade, and the upper end of the rod is joined to theblade 30, between the ends of the blade, by an adjustable nut 46. Apreloaded compression spring 48, positioned between the base 20 and theblade 30, urges the blade 30 upwardly to maintain the blade inengagement with the nut 46.

As well known to those skilled in the art, the bimetallic elements 42and 44 of the temperature sensing device 40 will expand or contract inresponse to the temperature changes of the surrounding environment.Thus, by the above-described arrangement, the rod element 44 will exerta force on the blade 30, through the adjusting nut 46, which is a directfunction of the environmental temperature sensed by the device 40 andthe spring rates of the spring 48 and the blade 30. Further, the nut 46permits the zero setting of the transmitter temperature sensing deviceto be adjusted.

In accordance with this invention, the transmitter 10 also includes amovable exhaust nozzle assembly 50, through which the fluid in thechamber 22 can be exhausted. The assembly 50 is positioned on thetransmitter base 20 below the free end 34 of the blade 30 and is capableof translating on the base 20 longitudinally with respect to the blade.

The illustrated assembly 50 in accordance with this invention includes ahollow valve seat member 52 which is s'lidably engaged with the topsurface of the base 20, and which extends transversely across the freeend 34 of the blade 30. This arrangement places the interior of themember 52 in fluid communication with the conduit 25connected to thepressure chamber 22. As indicated in FIGS. 1 and 4, one end of themember 52 is pivotally secured to the base 20 by a pivot pin 54, whilethe other end of the member 52 is free to slide on the base 20 through apredetermined are. A brace 51 can be provided on the member 52 toprotect the free end 34 of the arm 30 from damage during storage orshipment.

. The are through which the free end of the member 52 slides iscontrolled by providing that end of the member with a pin 55 whichengages within an arcuate slot 29 provided in the base 20. The limits ofthe slot 29 are selected so that the interior of the member 52 remainsin fluid communication with the conduit 25 as a member 52 is movedbetween its extreme positions (see FIGS. 4 and 5). A pointer 57 can beprovided on the free end of the member 52, and scale markings 27 can bearranged on the base adjacent the slot 29 to indicate the relativeposition of the member 52. A suitable gasket material such as an O-ring53 is provided to seal the member 52 against the base 20, and therebyassure that the interior of the member 52 is in sealed fluidcommunication with the pressure chamber 22 through the conduit 25.

The assembly 50 also includes a valve seat 56 mounted in the center ofthe seat member 52 directly below the free end 34 of the blade 30. Theseat 56 defines an exhaust port 58 through which the fluid from thechamber 22 can exhaust during the operation of the transmitter. Further,a ball valve 60 is positioned in the upper outlet end of the port 58 andis capable of moving within the port to control the rate of flow offluid through the port. As indicated in FIG. 2, the ball valve 60 isengaged with the free end 34 of the blade 30. By this arrangement, thetransmitter is adapted so that the force transmitted to the ball valve60 through the blade 30 changes the balance of forces on the ball valvedue to the blade and the pressure of the fluid in the chamber 22, andchanges the position of the ball valve within the port 58. The force ofthe blade 30 on the ball valve 60 thereby controls the pressure in thechamber 22 by varying the rate at which fluid will exhaust from thechamber through the port 58.

A modified transmitter 10A, constructed in accordance with thisinvention, is illustrated in FIG. 5. The structure of the transmitter10A is essentially the same as in the abovedescribed transmitter l0, andthe same reference numerals have been used in FIG. 5 to identify thecommon components. The transmitter 10A differs from the transmitter It)to the extent that the rigid bulb temperature sensing device 410 of thetransmitter 10 is replaced by a conventional remote bulb temperaturesensing device 70 in the transmitter 10A.

As shown in FIG. 5, the temperature sensing device 70 includes a bulb 72which is filled with a thermally expansive fluid. The bulb 72 thus canbe placed at a point remote from the transmitter 10A, and the fluid inthe bulb will sense the temperature at that point. A fluid conduit 74connects the remote bulb 72 to a flexible diaphragm 76 mounted on thetransmitter 10A. By this arrangement, the change in pressure in the bulb72 resulting from the expansion of the fluid therein will be transmittedto the diaphragm 76 and will cause an expansion of the diaphragm inaccordance with the temperature sensed by the bulb.

The lower portion of the diaphragm 76 includes a protrusion 77 whichengages with the cantilevered blade 30 between the ends of the blade.The protrusion 77 thereby transmits a force to the blade 30, against theresistance of the preloaded spring 418, in proportion to the expansionof the diaphragm 76. In this manner, the diaphragm 76 subjects the blade30 to a force which is directly related to the temperature sensed by theremote bulb 72 and the spring rates of the spring 48 and the blade 30.An adjusting screw 78 is engaged with the top portion of the diaphragm76, and pennits the zero setting of the temperature sensing device 70 tobe adjusted.

During the operation of the transmitter, in accordance with thisinvention, the chamber 22 is connected to a fluid pressure source and aremotely located receiver gauge through an upstream restriction. Thesupply fluid is continuously exhausted from the chamber 22 through theconduit and the port 58. The rate of exhaust of the fluid, and thus thepressure in chamber 22, is controlled by the force applied to the ballvalve 60 by the free end of the blade 30. A variation in the force ofthe blade on the ball 60 will thus vary the rate of exhaust andcorrespondingly adjust the pressure in the chamber 22.

In addition, the temperature at the point being controlled is sensed andconverted to a corresponding force on the blade 30 by the temperaturesensing means provided on the transmitter. For instance, in theembodiment shown in FIGS. 14, an increased temperature sensed by thebimetal elements 42 and 44 will expand the elements, and the elementswill transmit an increased force to the blade 30 through the adjustingnut 46. In the embodiment shown in FIG. 5, an increased temperaturesensed by the remote bulb 72 expands the bulb and the connecteddiaphragm 76, and the diaphragm 76 will transmit an increased force tothe blade 30 through the protrusion 77. In both embodiments the blade 30in turn transmits the increased force of the temperature sensing devicesto the ball valve 60 of the exhaust nozzle assembly 50 through asubstantial lever arm "L" defined by the blade (see FIG. 2). The forceon the ball valve 60 and the rate of exhaust of the fluid from thechamber 22 are varied in direct relation to the temperature sensed bythe transmitter. This action thereby varies the pressure in the chamber22 proportionately so that the connected receiver gauge indicates thesensed temperature.

From the above description of the transmitter, in accordance with thisinvention, it is evident that the span of the transmitter is a functionof the length of the lever arm "L" through which the force of the blade30 acts upon the ball valve 60 of the exhaust nozzle assembly 50. Inaccordance with this invention, the span of the transmitter can beadjusted by pivoting the movable nozzle assembly 50 about the pivot pin54 to move the ball valve 60 longitudinally with respect to the blade 30and thereby change the effective length of the blade lever arm "L". Forinstance, the assembly 50 can be pivoted from its normal position asshown in FIG. 1 to an outward position such as shown in FIG. 4, toincrease the length of the lever arm "L" and correspondingly increasethe span. Alternatively, the assembly 50 can be pivoted inwardly into aposition such as shown in FIG. 5 to decrease the lever arm "L" andthereby increase the span.

Although the transmitter in accordance with this invention has beendescribed above with reference to two particular embodiments, it shouldbe understood that the present disclosure has been made only by way ofexample. Consequently, numerous changes in the details of constructionas well as in the modes of utilization will be apparent to those skilledin the art and may be resorted to without departing from the spirit andscope of the invention as claimed.

I claim:

I. A temperature actuated pressure transmitter comprising:

a. a base member;

b. a cantilevered blade having a fixed end secured to said base memberand a longitudinally extending free end;

c. a pressure chamber provided adjacent the free end of said blade andadapted to be connected to a fluid pressure system;

d. a movable exhaust nozzle assembly arranged in sealed fluidcommunication with said pressure chamber, said nozzle assembly includingan exhaust port adapted to exhaust the fluid from said pressure chamberand a valve member operatively engaged with the free end of said bladeand adapted to vary the flow of exhaust fluid through said port inaccordance with the force applied to said valve member by said blade,said exhaust nozzle assembly being adjustably movable longitudinally ofsaid longitudinally extending free end of blade; and

e. temperature sensing means engaged with said blade intermediate itsends for exerting a force on said valve member through the lever arm ofsaid blade, to thereby adjust the valving action of said valve memberand change the fluid pressure in said pressure chamber in proportion tothe temperature sensed by said sensing means;

whereby said exhaust nozzle assembly can be translated longitudinallywith respect to said longitudinally extending free end of said blade toselectively adjust the effective lever arm through which said blade actsupon said valve member and thereby adjust the span of said transmitter.

2. A temperature actuated pressure transmitter in accordance with claim1 wherein said movable exhaust nozzle assembly comprises valve seatmeans slidably engaged with said base member in sealed fluidcommunication with said pressure chamber and defining an exhaust porthaving an outlet adjacent said free end of said blade, and wherein saidvalve member comprises a ball valve positioned in said exhaust port andengaged with the free end of said blade, with said ball valve beingadapted to change the rate of exhaust of fluid through said port andthereby change the pressure in said chamber in proportion to the forceapplied to said ball valve by said blade.

3. A temperature actuated pressure transmitter in accordance with claim2 wherein said ball valve is arranged in said exhaust outlet port torestrict the flow of exhaust through said port and thereby increase thepressure in said chamber in response to an increase in the force appliedto said valve by said blade.

4. A temperature actuated pressure transmitter in accordance with claim1 wherein said nozzle assembly is pivoted at one end so as to extendtransversely across the free end of said blade such that pivotalmovement of said nozzle assembly through a predetermined are effectivelyvaries the lever arm length through which said blade acts upon saidvalve member.

5. A temperature actuated pressure transmitter comprising:

a. a base member;

b. a cantilevered blade having one end fixed to said base member andhaving a longitudinally extending free end;

c. a pressure chamber provided in said base member adjacent the free endof said blade and adapted to be connected to a fluid pressure source;

d. a longitudinally movable exhaust nozzle assembly pivoted to said basemember adjacent said free end of said blade and in fluid communicationwith said pressure chamber, said nozzle assembly including a valve seatdefining an exhaust port adjacent said blade member and furtherincluding a valve positioned within said port in engagement with thefree end of said blade and adapted to vary the exhaust of fluid throughsaid port in response to a force ap plied to said valve by said blade,said exhaust nozzle assembly being adjustably movable longitudinally ofsaid longitudinally extending free end of said blade;

e. means sealing said nozzle assembly with respect to said base member;and

f. a temperature responsive element engaged with said blade intermediateits ends and adapted to exert a force on said blade in proportion to asensed temperature so that said blade exerts a proportionate force onsaid valve through a lever arm and said element and said blade cooperateto change the pressure in said chamber in proportion to the temperaturesensed by said element by varying the exhaust through said port;

whereby said exhaust nozzle assembly can be translated longitudinallywith respect to said longitudinally extending free end of said blade toselectively adjust the effective lever arm through which said blade actsupon said valve member and thereby adjust the span of said transmitter.

6. In a temperature actuated pressure transmitter including a bladehaving a longitudinally extending free end, a temperature sensing meansadapted to transmit a force to said blade in accordance with a sensedtemperature, and a pressure chamber adapted for connection with a fluidpressure system, the improvement comprising a movable exhaust nozzleassembly which permits the span of the transmitter to be adjusted, saidassembly comprising:

a. a valve seat arranged for translation longitudinally of saidlongitudinally extending free end of said blade while being maintainedin sealed fluid communication with said chamber;

b. an exhaust port defined in said seat through which the fluid can beexhaust from said chamber; and

c. a valve member positioned within said port and operatively engagedwith the free end of said blade so that a force transmitted to saidvalve member through the lever arm of said blade varies the flow ofexhaust fluid through said port and thereby varies the pressure in saidchamber;

whereby the pressure in said chamber changes in response to thetemperature sensed by said sensing means and said nozzle assembly can betranslated longitudinally with respect to said longitudinally extendingfree end of said blade to selectively adjust the effective lever armthrough which said blade acts on said valve member and thereby adjustthe span of said transmitter.

7. A physical condition actuated pressure transmitter comprising:

a. a base member;

b. a cantilevered blade having a fixed end secured to said base memberand a longitudinally extending free end;

c. a pressure chamber provided adjacent the free end of said blade andhaving an inlet port for connection to a fluid pressure system;

d. a movable force balance exhaust nozzle assembly arranged in sealedfluid communication with said pressure chamber, said nozzle assemblyincluding an exhaust port for exhaust of fluid from said pressurechamber and a valve member operatively engaged with said longitudinallyextending free end of said blade for varying the flow of exhaust fluidthrough said port in accordance with the force applied to said valvemember by said blade, said exhaust nozzle assembly being adjustablymovable longitudinally of said longitudinally extending free end of saidblade; and

e. physical condition sensing means engaged with said blade intermediateits ends for exerting a force on said valve member through the lever armformed by said blade which force varies as a function of the magnitudeof the physical condition sensed by said physical condition sensingmeans to thereby adjust the valving action of said valve member to varythe fluid pressure in said pressure chamber as a function of themagnitude of the physical condition sensed by said physical conditionsensing means;

whereby said exhaust nozzle can be translated longitudinally withrespect to said longitudinally extending free end of said blade toselectively adjust the effective lever arm through which said blade actsupon said valve member and thereby adjust the span of said transmitter.

1. A temperature actuated pressure transmitter comprising: a. a basemember; b. a cantilevered blade having a fixed end secured to said basemember and a longitudinally extending free end; c. a pressure chamberprovided adjacent the free end of said blade and adapted to be connectedto a fluid pressure system; d. a movable exhaust nozzle assemblyarranged in sealed fluid communication with said pressure chamber, saidnozzle assembly including an exhaust port adapted to exhaust the fluidfrom said pressure chamber and a valve member operatively engaged withthe free end of said blade and adapted to vary the flow of exhaust fluidthrough said port in accordance with the force applied to said valvemember by said blade, said exhaust nozzle assembly being adjustablymovable longitudinally of said longitudinally extending free end ofblade; and e. temperature sensing means engaged with said bladeintermediate its ends for exerting a force on said valve member throughthe lever arm of said blade, to thereby adjust the valving action ofsaid valve member and change the fluid pressure in said pressure chamberin proportion to the temperature sensed by said sensing means; wherebysaid exhaust nozzle assembly can be translated longitudinally withrespect to said longitudinally extending free end of said blade toselectively adjust the effective lever arm through which said blade actsupon said valve member and thereby adjust the span of said transmitter.2. A temperature actuated pressure transmitter in accordance with claim1 wherein said movable exhaust nozzle assembly comprises valve seatmeans slidably engaged with said base member in sealed fluidcommunication with said pressure chamber and defining an exhaust porthaving an outlet adjacent said free end of said blade, and wherein saidvalve member comprises a ball valve positioned in said exhaust port andengaged with the free end of said blade, with said ball valve beingadapted to change the rate of exhaust of fluid through said port andthereby change the pressure in said chamber in proportion to the forceapplied to said ball valve by said blade.
 3. A temperature actuatedpressure transmitter in accordance with claim 2 wherein said ball valveis arranged in said exhaust outlet port to restrict the flow of exhaustthrough said port and thereby increase the pressure in said chamber inresponse to an increase in the force applied to said valve by saidblade.
 4. A temperature actuated pressure transmitter in accordance withclaim 1 wherein said nozzle assembly is pivoted at one end so as toextend transversely across the free end of said blade such that pivotalmovement of said nozzle assembly through a predetermined arc effectivelyvaries the lever arm length through which said blade acts upon saidvalve member.
 5. A temperature actuated pressure transmitter comprising:a. a basE member; b. a cantilevered blade having one end fixed to saidbase member and having a longitudinally extending free end; c. apressure chamber provided in said base member adjacent the free end ofsaid blade and adapted to be connected to a fluid pressure source; d. alongitudinally movable exhaust nozzle assembly pivoted to said basemember adjacent said free end of said blade and in fluid communicationwith said pressure chamber, said nozzle assembly including a valve seatdefining an exhaust port adjacent said blade member and furtherincluding a valve positioned within said port in engagement with thefree end of said blade and adapted to vary the exhaust of fluid throughsaid port in response to a force applied to said valve by said blade,said exhaust nozzle assembly being adjustably movable longitudinally ofsaid longitudinally extending free end of said blade; e. means sealingsaid nozzle assembly with respect to said base member; and f. atemperature responsive element engaged with said blade intermediate itsends and adapted to exert a force on said blade in proportion to asensed temperature so that said blade exerts a proportionate force onsaid valve through a lever arm and said element and said blade cooperateto change the pressure in said chamber in proportion to the temperaturesensed by said element by varying the exhaust through said port; wherebysaid exhaust nozzle assembly can be translated longitudinally withrespect to said longitudinally extending free end of said blade toselectively adjust the effective lever arm through which said blade actsupon said valve member and thereby adjust the span of said transmitter.6. In a temperature actuated pressure transmitter including a bladehaving a longitudinally extending free end, a temperature sensing meansadapted to transmit a force to said blade in accordance with a sensedtemperature, and a pressure chamber adapted for connection with a fluidpressure system, the improvement comprising a movable exhaust nozzleassembly which permits the span of the transmitter to be adjusted, saidassembly comprising: a. a valve seat arranged for translationlongitudinally of said longitudinally extending free end of said bladewhile being maintained in sealed fluid communication with said chamber;b. an exhaust port defined in said seat through which the fluid can beexhaust from said chamber; and c. a valve member positioned within saidport and operatively engaged with the free end of said blade so that aforce transmitted to said valve member through the lever arm of saidblade varies the flow of exhaust fluid through said port and therebyvaries the pressure in said chamber; whereby the pressure in saidchamber changes in response to the temperature sensed by said sensingmeans and said nozzle assembly can be translated longitudinally withrespect to said longitudinally extending free end of said blade toselectively adjust the effective lever arm through which said blade actson said valve member and thereby adjust the span of said transmitter. 7.A physical condition actuated pressure transmitter comprising: a. a basemember; b. a cantilevered blade having a fixed end secured to said basemember and a longitudinally extending free end; c. a pressure chamberprovided adjacent the free end of said blade and having an inlet portfor connection to a fluid pressure system; d. a movable force balanceexhaust nozzle assembly arranged in sealed fluid communication with saidpressure chamber, said nozzle assembly including an exhaust port forexhaust of fluid from said pressure chamber and a valve memberoperatively engaged with said longitudinally extending free end of saidblade for varying the flow of exhaust fluid through said port inaccordance with the force applied to said valve member by said blade,said exhaust nozzle assembly being adjustably movable longitudinally ofsaid longitudinally extending free end of said blade; and e. Physicalcondition sensing means engaged with said blade intermediate its endsfor exerting a force on said valve member through the lever arm formedby said blade which force varies as a function of the magnitude of thephysical condition sensed by said physical condition sensing means tothereby adjust the valving action of said valve member to vary the fluidpressure in said pressure chamber as a function of the magnitude of thephysical condition sensed by said physical condition sensing means;whereby said exhaust nozzle can be translated longitudinally withrespect to said longitudinally extending free end of said blade toselectively adjust the effective lever arm through which said blade actsupon said valve member and thereby adjust the span of said transmitter.